The 50/50 Rule

Much is made in the business world about the 80/20 rule.  Also known as the Pareto principle, the basic idea is that in many phenomena 80% of consequences stem from 20% of the causes.  Wikipedia has a good discussion of the principle, its myriad applications, and its common misuse and abuse.  (I should have called this post “The Principle of Factor Sparsity”; that would definitely have merited an honorary doctorate down the road…)

80/20 and its variants play an almost mythical role in all facets of mainstream software design.  You’ll hear that 80% of users only use 20% of the features.  Or that 20% of bugs account for 80% of the problems people find in released software.  Of course, none of the numbers are exact, and people are quick to point out that the principle is in effect even when the numbers aren’t exactly close.

For example, it turns out that it’s more like 5% of the crashing bugs account for 95% of the error reports people send.  Is this still the 80/20 rule?  Can I just substitute any numbers and there’s still some validity to the model?  If so, I’ll coin the Harris Principle–that X% of consequences stem from Y% of the causes.  It’s bound to be applicable to an even wider array of scenarios!

Sarcasm aside, there is something valid to be learned from the 80/20 rule.  In general, in mainstream software, we do try to design around how the majority of people expect it to work.  In such a broadly used tool as Word or Excel, we hope we can suit more like 90% or even 98% of the people; the value of the data we gather from the Customer Experience Improvement Program is that we really can tell how we’re doing.

One of the challenges of designing a piece of software for 400 million people is that even if you are extremely successful with a design–even if you totally hit it out of the park and delight 99% of your customers… well, you still have roughly the population of New Zealand who think you made the wrong decision.

The good news is that although most design decisions fall somewhere along the lines of 80/20, it doesn’t have to be a zero-sum game.  There’s often ways to satisfy the 80% and the 20% both because they work in different ways of have different expectations of the software.

For instance, sometimes the 80% are “normal” users and the 20% are “expert” users.  In order to satisfy both groups, you must determine how to enable expert-level functionality in a way that adds no complexity for people who have no need for it.  It can be done, but it takes some thought.

I think a good example of this is the “Lock Toolbar” feature in recent versions of Internet Explorer and Windows.  You can’t drag the toolbars around unless you right-click the toolbar and uncheck “Lock the Toolbars” on the context menu.

For “normal” people, the toolbars just work the right way.  They don’t move unexpectedly, and they don’t end up mysteriously disappearing or floating in the middle of the screen.  The software feels more predictable, and because most people don’t right-click on the toolbar, the complexity is hidden from them.

On the other hand, for the expert user like me who does want to move around their toolbars, finding the setting to unlock them is just a minor inconvenience.  The Windows taskbar adopted the same design in Windows XP and I believe this is a good thing.  (No more explaining to people how to get the taskbar back on the bottom of the screen!)

The hardest problem in user interface design is when you come face to face with the 50/50 rule.  Although rare, occasionally you will discover a a situation in which the needs and wants of half of your customers are diametrically at odds with that of the other half.

Here’s a simple example of a 50/50 scenario in the Outlook keyboarding model.  Everyone in the world knows that CTRL+F performs Find within a program, right?

Well, actually, that’s the newfangled shortcut, standardized around 1993.  Before that, most programs used F4 as the standard shortcut for Find.  (Just like CTRL+X, C, and V used to be Shift+Del, Ctrl+Ins, and Shift+Ins before they were changed in Windows 3.1.)

So, with F4 firmly cemented as the shortcut for Find, early 1990s-era Microsoft electronic mail products used CTRL+F for Forward.  Of course, forwarding e-mail being one of the most common things you do in a mail program, in retrospect that design decision makes perfect sense.

Fast forward to today.  Millions of loyal customers have learned to rely on CTRL+F in Outlook to forward mail and brace at the thought of it going away.  Millions more are confused by their inability to use CTRL+F to Find in Outlook and can’t understand why new mail windows keep popping up.  “F4?!?!?” they gristle under their breath.

What to do?  If you change CTRL+F to Find, millions of people have their productivity impacted for no positive gain at all.  If you don’t, millions of people are confused by your software and find it hard to use.  Of course, you could make it a customizable option, but experience and data show that hardly anyone would think they could change it.  There’s no easy way to satisfy both groups out-of-the-box.

When the 50/50 rule bites you, it leaves a mark.

Comments (33)

  1. John C. Kirk says:

    Personally, I find it annoying that Ctrl-F doesn’t do what I expect, but I can live with a different shortcut. What’s more annoying is that F3 doesn’t do the standard "repeat last search" function, and that it doesn’t seem to serve any other purpose – I’d be interested to hear the story behind that (e.g. backwards compatibility).

    I do remember that F5 used to be the "check mail" key, then it became F5 or F9, and now only F9 works (which confused some of my colleagues after we upgraded to Outlook 2003). Could you do something similar with forwarding? Presumably if you assigned Ctrl-F to "Find" then you’d need a different shortcut for "Forward", so as a short-term approach I’d say "Use Ctrl-F or [new shortcut]" to forward. No inconvenience to existing users, but if you encourage new users to use the new shortcut then eventually you can reassign Ctrl-F.

  2. on says:

    Dear Jensen Harris, (excuse me for being off-topic)

    Your blog is so interesting.

    Please could you make other MS bloggers to write as interesting posts as yours? 🙂

    In fact i would like to read another blog focusing on the Vista UI where i can understand MS decisions (about the UI).

    The WinUX blog is empty, the AERO blog (mentioned in the UI guidelines) doesn’t exist.

  3. Why not prompt the person the first time they press Ctrl-F?

    Do you want search, or forward? With a remember me check box.

    Or maybe ask them if they press ctrl-f then close the new mail window straight away – a clear sign that it was not what they wanted to do.

    Best regards


  4. "What to do?" Change CTRL+F to find or leave it? In the Danish versions of recent Office programs CTRL+F is used for "bold" (F from the danish word "fed").

    As a consultant and web professional I work on English version on my laptop and Danish version at a customer. And I can tell you that it’s absolutely ANNOYING when the shortcuts change.

    Furthermore, "find" in the Danish version of Internet Explorer is CTRL+B.

    My point here is that frustrations come from inconsistency. Whenever things change, it’s frustrating – and i’ve seen this with both expert users and novice users.

    The choice between what to do is a hard one. One thing is for sure. I think you can rule out anything in between as a solution. It’s either change or not.

  5. Tim says:

    "If so, I’ll coin the Harris Principle–that X% of consequences stem from X% of the causes. It’s bound to be applicable to an even wider array of scenarios!"

    If you really want it to apply to a wider range of scenarios, you might want to make it "X% of consequences stem from Y% of the causes."

    Kiss that honorary doctorate goodbye! 🙂

  6. bg says:

    "that X% of consequences stem from X% of the causes"

    you should Patent that!

  7. First I agree with Tim, but by the time anyone reads this Jensen will likely have caught that X – Y bit.

    As to the other comments I wanted to chime in on the keyboard shortcuts that are used presently (hey, Jensen, F4 doesn’t find!):

    – Ctrl+M also checks email in Outlook

    – F4 does not, to the best of my knowledge, activate the Find command in Outlook

    – Believe it or not, F3 and Alt+I bring up the find command to search in the current folder (notice that it toggles the bar at the top of the folder)

    – Ctrl+Shift+F brings up the advanced Find command (defaulting to the current Outlook area, like calendar items or messages) (To set the default Advanced Find to search everything you need to save your search and then hotkey it with a global shortcut…before full text search, that was the way to go)

    As for the this whole issue about Ctrl+F, I say keep it the way it is. After all, Ctrl+F does work to search within an email itself–as Word is most likely one’s email editor. And, in my opinion, more and more users will be using Full Text search engines to perform global searches in the future–be they your product or the other one who just released a particular "Pack." For instance, aren’t you folks at Microsoft using Ctrl+Shift+M to use MSN to search your Outlook data? Even more, assigning something new to Ctrl+F brings up the question of whether to load the Advanced Find or the current-folder-find. I say leave it as it is and let Vista’s (eventual file system) or MSN Search’s full text search be the Find of choice for your round of users who utilize keyboard shortcuts.

    Thank for you the great post and blog, Jensen. Glad to hear how much thought you all are pointing into your decisions. If only Beta 1 were in just a little bit more stable shape… 🙂

  8. ChrisC says:

    Tim (et. al.)

    If you really want it to apply to a wider range of scenarios, you might want to make it "X% of consequences stem from Y% of the causes."

    I think he meant what he wrote.

    Note that the X% … X% follows this sentence:

    [quote] For example, it turns out that it’s more like 5% of the crashing bugs account for 95% of the error reports people send. Is this still the 80/20 rule? [/quote]

    In other words if 80/20 == 95/5 then why not just dispose of fictional accuracy and use the same variable name.

    Jensen has corrected himself before… I’m sure if he meant to use a "Y" he`ll admit it 🙂

    -Chris C.

  9. Hmmm it does not look like my trackback worked, so here it is typed in manually:

    After reading this post and some of the comments it got me thinking about the problem concerning keyboard shortcuts that Jesper Rønn-Jensen pointed out (the issue with internationalization). And I could not resist writing a post about it:

  10. jensenh says:

    F4 does perform a search when you have a mail open. That it doesn’t in the main Outlook shell is a little weird.

    The "F3 to Find Next" thing isn’t really used in Office, but there are programs I use which do use this, such as RegEdit…

  11. jensenh says:


    You could definitely prompt, and in one similar case (CTRL+ENTER to send e-mail in Outlook 12) the Outlook team did exactly that.

    But do you really want dialog boxes coming up for many of the efficient keystrokes you use? Even once? And of course, there’s the problem that most people don’t tend to read dialog boxes or message boxes…

    So, technically, I’d agree with you this can be a solution in isolation. Long term, I don’t like where it takes us used in version over version…

  12. jensenh says:

    Re: X% of X%

    I originally had a second sentence which I edited out that said "Where both Xs are independent variables representing a percentage between 0% and 100%."

    But X and Y would have been even more clear. 🙂

  13. cw says:

    From what I recall…

    The CTRL-F brouhaha happened in the Win95 timeframe. MS Mail used CTRL-F. Win95’s (Chicago) email client (Capone) had to change to the new Win95 look-n-feel. This included CTRL-F for Find.

    Then BillG started complaining that he’s always trying to FIND steveb (Steve Ballmer) instead of forwarding email to steveb.

    When BillG complains, things usually happen.

  14. jensenh says:


    That’s a good read. Internationalization of keyboard shortcuts is an interesting topic.

  15. John C. Kirk says:

    Hmm, now you come to mention it, you’re right about F3 not being common anywhere in Office. I’m primarily a VB developer, so I use that shortcut a lot inside the Visual Studio IDE, and in Notepad. In fact, I do remember getting messages in Word about "such-and-such is not a valid Autotext entry", so I guess that F3 is primarily used for that.

  16. Joe Surfer says:

    Control-F should Find in Outlook, because that’s what Control-F does in every other application. Outlook is the odd-man-out here.

    Who uses just Outlook, and no other office product? Almost nobody. So almost all Outlook users know that Control-F is used to Find.

    This isn’t a 50-50 rule, this is a 99-1 rule.

    Those 1% who want the current behavior can edit their control key settings. (Presumably Bill knows how to do that, right? Or maybe just check the username at install time, and if it’s billg set the default to his preference.)

  17. Hanford says:

    Excellent post, Jensen.

    Occasionally an "expert" feature can haunt the casual user. Now if an IE toolbar does get moved somehow — let’s say Norton anti-virus gets installed and it’s toolbar pushes everything out of shape — it’s now even harder for the casual user to figure out how to restore it if the "lock" option is on. I still think IE is better off with the Lock option, but it’s one of the hangups of offering expert modes and controls.

  18. Captain Carbohydrate says:

    In IE, F3 does "search ‘My Videos’ on local disk" or some psychotic thing like that. (I don’t know what directory it is; it’s one of those "My SomethingOrOther" "folders" that Office obsessively tries to ram down your throat — the booby-trap bug where it can’t keep track of the current working directory).

    Yeah, when I want to search for text files in a source tree on my disk, the first thing that occurs to me is to start up a WEB BROWSER and tell it to "search again for text in current page", in the hope that it’ll play an "application busy" animation of a stupid dog (even though it’s doing absolutely nothing) as it prompts me to search an empty system directory that I’ve never saved a file to in my life, except by accident.

    How am I supposed to guess that the way to find files is to search for text in a web page? Why not hide search-for-files in the ODBC configuration dialog in the control panel? Then you could put ODBC config in a utility invoked by double-clicking a file named "Play Dog Animation", located in "My Documents".

  19. I’m not sure I see why there’s a problem with prompting. If you did something like:

    – Assign a new shortcut for "Forward"

    – Refer only to the new shortcut in tooltips and other UI elements so that the only people who press Ctrl+F are people with a prior expectation of its meaning

    – The very first time a user presses "Ctrl+F", display a dialog box like this:

    "This is the first time you have pressed Ctrl+F in this version of Outlook. In previous versions, Ctrl+F meant Forward, but in other programs Ctrl+F usually means Find.

    You can always use (whatever) for Forward and F4 for Find.

    What do you prefer Ctrl+F to mean?"

    [ Forward ] [ Find ]

    I don’t see any reason for offering the option *not* to remember the selection, it would only complicate the dialog box, and what are the chances that someone would want Ctrl+F to do both those things alternately?

    And by having the buttons be "Forward" and "Find", the user doesn’t have to read the text at all, just what’s on the buttons. And if they’re pressing Ctrl+F they’re probably pressing it because they expected one of those things so they’ll know exactly which one to press.

    A dialog box that happens exactly once per user, which is at worst mildly annoying on a once-off basis, seems like a clear win versus annoying 50% of your users on a daily basis as long as they use the product.

  20. Michael Zuschlag says:

    I think Joe Surfer has a point. 50% of your users may expect Crtl-F to Forward, but they are likely to at least be aware that Ctrl-F can mean Find. The complement cannot be said of the other 50% regarding F4.

    And while 50% of current users expect Ctrl-F to be Forward due to previous use of Outlook, it would seem that nearly 100% of all *future* new users would expect it to be Find, at least until they’re indoctrinated to think it’s Forward, (thus perpetuating the problem). So, with new users coming on board that tips the balance: you’d confuse less users in aggregate by changing it to Find. It’s a tough call, but I think suite consistency trumps legacy consistency in this conflict.

    BTW, in the main Outlook shell, "Find" is Ctrl-E (as you know), but it’s not really Find –it’s Search. Maybe that’s why it isn’t quite consistent, not that it’s a particulary good reason.

  21. This has very little to do with your article, but I’m wondering about the future of task panes. In general they seem to take up a lot of screen space, and they’re often of very little use to me. In the screenshots I’ve seen there seem to be less lurking task panes around. That’s great.

    However, I’m curious about the future of the Word Styles & Formatting task pane which I do find very useful and keep open most of the time. I really like the ability to define a palette of 10 or so styles and use these throughout my document. How will styles be implemented in this next version of Word? I don’t really want to have to have the extra click of opening a drop down like back in Word97!

  22. sloan says:

    This whole thread is kind of funny. It just highlights how arbitrary shortcut keys are to begin with. F1 vs. Ctrl-F… come on, either of those can mean anything! Especially with so many functions to choose from you first have to determine which functions deserve keys (usually based on usage), and then which key combinations translate to what.

    The Office 12 approach of "quick keys" (I think that is what Jensen called it) is based on the hierarchy, but at least seems less arbitrary and more extensible. But this is a bit of putting the categorization before the function. (Not that this is a bad compromise)

    But what about people that KNOW exactly what function/action they want to commit, but it isn’t popular enough for a shortcut and is three levels deep? In the overall time it takes to just type "find" in a dedicated "actions" box, the user only has a penalty of time, and not assessing (changning mental context) 2 levels of icons and "quick key" letters evaluation.

    I am sure the group went through lots of ideas. If you went through this though and did some testing I’d love to hear it. In general, an entry about ideas that you discarded due to testing would be just as valuable as those you kept!

    Keep up the good work!

  23. Oh, and how I am one of those people cursing that F4 key.

    Poor website design has made me increasingly dependent on Ctrl-F just to find key words on a page (find-as-you-type solutions like FireFox has really tickle me), and I’ve watched as that impulse has spread to other applications.

    What a pity F4 doesn’t launch find in IE.

    At least I know the rational now.

  24. josh says:

    I *still* use Shift-Del, Ctrl-Ins, and Shift-Ins… not F4 though.

  25. BradA says:

    You had me the whole way — I thought for sure you were going to tell me the how to design my way out of the 50/50 rule… but all I get is "When the 50/50 rule bites you, it leaves a mark"

    Oh well… I still have that Susan B Anthony dollar around here somewhere…


  26. I’m with Josh – Shift-Del, Ctrl-Ins, and Shift-Ins are ingrained in my psyche because I find them much easier to hit than ctrl+x/c/v due to the space on the left of Ins/Del. A few modern apps are starting to remove those shortcuts and I hate them for it.

    It is for this reason that I absolutely despise the new keyboard styles with the massive del key and no insert except on the numpad 🙂

  27. pli7 says:

    On the topic of keyboard shortcuts, I’m wondering if your usage data shows how often people actually use key combos such as Ctrl-Alt-X, Alt-Shift-F2, etc.

    I, for one, never use such key combos because they are hard to press and difficult to remember and confusing. And I’ve never seen any friend or coworker use these combos. Just wondering.

  28. cw says:

    Joe Surfer wrote:

    "Control-F should Find in Outlook, because that’s what Control-F does in every other application. Outlook is the odd-man-out here.

    Who uses just Outlook, and no other office product? Almost nobody. So almost all Outlook users know that Control-F is used to Find.

    This isn’t a 50-50 rule, this is a 99-1 rule. "

    You’re writing this in 2006. Back in 1993-1994 when Capone was developed, CTRL-F was NOT the de facto keyboard shortcut for Find, unless you were used to using Macs.

  29. Stephen McLaren says:

    I remember when I first made the switch from the Acorn OS (every school in the UK had them!) to Windows and being incredibly frustrated that Ctrl-S "didn’t work properly".

    I was so used to Ctrl-S changing the case of the selected text that I spent a long time saving my document every minute or so. This was on Office ’97 which if I recall correctly didn’t autocorrect capitilisation errors…

  30. ErickThompson says:

    This seems like the perfect place to use a dialog prompt on the first use. The first time a user uses control-F, ask them what action they want it to perform. That way, both groups get the functionality that they want.

    I would personally love to see this, as I hit ctrl-F to do a find all the time, as I spend most of my day in Visual Studio.


  31. It bites but so what??? says:

    So there is a reason behind why the short cut keys ended up the way they did. I could not care less. (Except it is a good example for this article)

    The only thing I want to know is where I can find a hack or a registry setting that will let me use CTRL+F for find, as I would in any other normal application. You can customize all other Office applications in various ways so why is Outlook so crappy???

  32. Does anyone else find the fact that you have to do an F4 in Outlook to Find something extremely annoying? …